Huh ... C behavior

[sanjaymeher]

Copy paste and run the example now remove the comment /*test2();*/
in main function ... Its not working .. Whyyyy ?? Behavior is really
queer !!!! I know the method

"int addDynamicMemory1(char *ptr, int size)" is not the right context
of use here But I want to get the solution to this particular problem



#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void test1();
void test2();
int addDynamicMemory1(char *ptr, int size);
int addDynamicMemory(char **ptr, int size);

int addDynamicMemory1(char *ptr, int size)
{
/* See and chek whether size memory is available or not */
int currSize;
if(ptr == NULL)
{
ptr = (char*) malloc(size * sizeof(char));
if(ptr != NULL)
{
printf("Initialized memory as null \n");
return -1;
}
else
{
printf("Can not Initialized memory as null \n");
return -1;
}
}

currSize = strlen(ptr);
size = currSize + size;
ptr = (char*) realloc(ptr, size*sizeof(char));

if(ptr != NULL)
{
printf(" re Allocation size is %d\n",size);
return 0;
}

printf(" re Allocation failed \n");
return -1;
}

int addDynamicMemory(char **ptr, int size)
{
/* See and chek whether size memory is available or not */
int currSize;
if(*ptr == NULL)
{
*ptr = (char*) malloc(size * sizeof(char));
if(*ptr != NULL)
{
printf("Initialized memory as null \n");
return -1;
}
else
{
printf("Can not Initialized memory as null \n");
return -1;
}
}

currSize = strlen(*ptr);
size = currSize + size;
*ptr = (char*) realloc(*ptr, size*sizeof(char));

if(ptr != NULL)
{
printf(" re Allocation size is %d\n",size);
return 0;
}

printf(" re Allocation failed \n");
return -1;
}

int main(void)
{
test1();
/*test2();*/
}

void test2()
{
char *test = NULL;

addDynamicMemory(&test, 40);
printf("At first test value is %s\n",test);
strcpy(test,"444444444");
printf("After allocation val is %s\n", test);

addDynamicMemory1(test, 60);
strcat(test,"666666666666");
printf("After allocation val is %s\n", test);

addDynamicMemory1(test, 60);
strcat(test,"888888888888888");
printf("After allocation val is %s\n", test);
}

void test1()
{
char *test = NULL;

addDynamicMemory(&test, 40);
printf("At first test value is %s\n",test);
strcpy(test,"444444444");
printf("After allocation val is %s\n", test);

addDynamicMemory(&test, 50);
strcat(test,"5555555555");
printf("After allocation val is %s\n", test);

addDynamicMemory1(test, 60);
strcat(test,"666666666666");
printf("After allocation val is %s\n", test);

addDynamicMemory1(test, 60);
strcat(test,"888888888888888");
printf("After allocation val is %s\n", test);
}

 

[Chuck F.]

Copy paste and run the example now remove the comment
/*test2();*/ in main function ... Its not working .. Whyyyy ??
Behavior is really queer !!!! I know the method

.... snip lots ...

It is working correctly according to the C standard. Undefined
behaviour allows anything whatsoever to happen, including "working"
(whatever that may be).

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